Altitude protection device

ABSTRACT

The invention relates to a device for protecting pilots and other crew members of high-performance aircrafts, especially people wearing pressure suits ( 1 ) according to the hydrostatic principle with veins ( 6 ) filled with liquid. Said device consists of a tension pocket ( 2 ) located in the region of the back and a pressure pocket ( 3 ) located in the abdominal region, airtight bladders ( 4 ) being inserted into both pockets. Said bladders ( 4 ) contain woven spacer elements ( 5 ) defining a minimum air volume in the bladders ( 4 ). In the event of falling ambient pressure, the pressure pocket ( 3 ) first expands and supports the breathing of the person wearing the device by means of pressure on the viscera, when pressure respiration appliances are used. If the ambient pressure falls further, the tension pocket ( 2 ) inflates and increases the peripheral tension in the pressure suit ( 1 ). In this way, for example, a decompression syndrome can be counteracted in the event of a sudden pressure drop in the cabin at high altitude.

The present invention relates to a device for providing altitudeprotection to pilots and other members of the crew of high-performanceaircraft, according to the precharacterising part of claim 1. Inparticular, this device to provide altitude protection relates towearers of acceleration protection suits that function according to thehydrostatic principle.

An altitude protection device is necessary when the pilot and any othercrew members are exposed to sudden loss of pressure in the cockpit of anaircraft flying at an altitude in excess of 12,200 metres above sealevel (FL400=flight level 40,000 ft). Be it that a technical defect hasled to the loss of pressure, that the cockpit cover has been destroyedor lost, or that emergency ejection has become necessary, in all thesesituations pressure stabilisation in the cockpit, which normallycorresponds to an air pressure at approximately 2,000 metres above sealevel (FL65), collapses. The higher the flight altitude during such anevent as mentioned, the closer the pressure-dependent boiling point ofaqueous solutions approaches the actual body temperature ofapproximately 37° C. of the pilot. Apart from gases, which expand in theintestines, and apart from decompression illness, which occurs despiterapid descent, the primary acute danger against which measures have tobe taken is, however, posed by hypoxemia, i.e. oxygen deficiency. Evenwhen breathing-in pure oxygen, at altitudes above 12,200 metres abovesea level (FL400) the O2 partial pressure is no longer sufficient toprevent hypoxemia. At this altitude, the time span during whichconsciousness permits useful actions is approximately 1.5 to 20 minutes,while 1000 m higher up, at an altitude of 13,100 metres above sea level(FL430) this time span is only 9 to 12 s. In order to counter the threatof hypoxemia, it is possible to breath pure oxygen, if need be even at apressure that is higher than the ambient pressure. In this context theterm “pressure breathing for altitude protection” (PBA) is used, incontrast to the newer “positive pressure breathing” (PPB). At analtitude in excess of 15,200 metres above sea level (FL500) pressurebreathing is of little value because it is physiologically impossible towithstand the necessary positive pressure to prevent severe hypoxemiawithout the presence of counter pressure. This is the reason why at thevery latest from this flight altitude persons must be equipped with apressure suit or altitude protection, which in the case of a sudden lossof pressure in the cabin immediately provides increased pressurisationto the body.

WO 03/020586 discloses an altitude protection device that is integratedin an acceleration protection suit according to the hydrostaticprinciple and, during sudden loss of pressure, pressurises the body ofthe wearer by increasing circumferential tension. The presentapplication represents the next state of the art.

The above-mentioned application uses a valve which during sudden largechanges in pressure closes immediately. Such a component is expensive,requires considerable maintenance effort to ensure its proper functionand still increases the susceptibility to trouble of the entire altitudeprotection device. This device with a valve is also associated with thecharacteristics that in the case of an accident the protection functionhas to be activated and is not a permanent feature from takeoff rightthrough to landing. During a slow continuous loss of pressure due to aminor leak in the envelope of the pressurised cabin, a valve that onlyreacts to quick changes in pressure will for example not close, andaltitude protection will have to be activated manually or by some othersystem.

It is the object of the present invention to create a supplementarydevice for an acceleration protection suit (hereinafter G-suit) whichdevice in conjunction with said G-suit is able to provide effectivealtitude protection in the above-mentioned cases in connection with aninsignificant increase in the dimensions of the G-suit. Furthermore, thetechnical and economic effort for this is to be as small as possible; inparticular there should be no need for any valves or other technicaldevices to activate the protection function at the moment when loss ofpressure occurs.

This object is met as set out in the characterising part of claim 1 inrelation to its essential characteristics, and in the further claims inrelation to further advantageous exemplary embodiments.

The subject matter of the invention is explained in more detail by meansof the enclosed drawings.

The following are shown:

FIG. 1 a diagrammatic representations of a first exemplary embodiment incross section at stomach height, pressurised at sea level;

FIG. 1 b diagrammatic representations of a first exemplary embodiment incross section at stomach height, with the circumferential tension of theG-suit commencing to increase;

FIG. 1 c diagrammatic representations of a first exemplary embodiment incross section at stomach height, at maximum extension of the twobladders;

FIG. 2 a, b cross sections of a first exemplary embodiment of a bladderin its expanded and relaxed state;

FIG. 3 a, b, c cross sections of a second exemplary embodiment of abladder in its relaxed, expanded and maximum expanded state; and

FIG. 4 a cross section of a third exemplary embodiment of a bladder withan additional gas reservoir.

FIG. 1 a, b, c diagrammatically shows a first exemplary embodiment ofthe inventive idea. It shows a cross section of the stomach region of aG-suit 1 according to the hydrostatic principle, for example accordingto EP 0 983 190. Said G-suit comprises for example four liquid-filledveins 6, two each on the front and on the rear of the G-suit 1. Theseveins 6 extend from the shoulder region of the G-suit 1 to the ankles;in each instance they provide the hydrostatic pressure that correspondsto the actual acceleration load. In this arrangement the veins 6 deformfrom an essentially flat lenticular cross section to a round one and inso doing tension the tension-resistant and stretch-resistant wovenfabric of the G-suit 1. By way of the tensile stress which is present inthis woven fabric as a result of the aforementioned, external pressureis built up on the body of the wearer, which external pressurecorresponds to the internal pressure.

FIG. 1 a shows the altitude protection device at atmospheric pressure atsea level. In the first exemplary embodiment shown, a pocket 2 isnon-positively attached in the back region of the G-suit 1, for exampleby sewing, comprising a textile fabric with characteristics that arecomparable to those of the G-suit 1. A bladder 4 has been placed in thispocket 2. This bladder 4, made of an elastic plastic material, forexample PU or PVC, is closed off on all sides towards the outside. Theexpansion of the bladder 4 is delimited by the pocket 2. As the pressurein the bladder 4 increases, the pocket 2 gradually assumes its maximumvolume with a circular cross section, and consequently thecircumferential tension increases as the circumference of the G-suit 1is shortened. For this reason, for better differentiation, the pocket 2is hereinafter referred to as the tension pocket 2. The simplest form ofa tension pocket 2, as shown in FIG. 1, comprises a piece of wovenfabric that lies flat against the inside of the G-suit 1 and that alongits edges is sewn to the G-suit 1. In this way part of the G-suit 1together with the additional piece of woven fabric forms a tensionpocket 2. However, it is also imaginable and covered by the invention toattach a closed pocket on the outside or the inside of the G-suit 1 in anon-positive manner. This pocket can be placed flat so that it is onlyattached by its edges, for example by sewing or gluing, or the entirearea resting on the G-suit 1 can be connected to said G-suit.

A pocket 3 is attached to the front of the G-suit 1, to the inside, forexample along a line that is perpendicular to the direction of tension,or to some points along this line. Attachment is such that expansion ofthe bladder 4 on the inside has essentially no influence on thecircumferential tension of the G-suit 1, but instead such that aninflated pocket 3 primarily exerts local pressure onto the body in placein the G-suit 1, more precisely to the soft tissue in the abdominalcavity. The pocket 3 is therefore hereinafter referred to as the“pressure pocket” 3. Attachment of the pressure pocket 3 is only usedfor positioning it in the desired location; attachment has to absorblesser tension than does attachment to the tension pocket 2. Theinventive step includes exemplary embodiments comprising severalpressure pockets 3 or tension pockets 2 arranged side by side.

One or several layers of a knitted or woven distance fabric 5 have beenplaced in both bladders 4, both in the tension pocket 2 and in thepressure pocket 3. Such knitted distance fabrics 5—at least partiallymade of monofilament material—are very flexible and deformable andmaintain their thickness even when subjected to loads per surface unit.The size and thickness of the knitted distance fabric 5 defines aminimum volume in the bladder 4, which minimum volume is taken up by therelaxed bladder 4 at base altitude, for example altitude at sea level.

Cockpits of fighter aircraft are designed as pressurised cabins. Duringclimbing flight of the aircraft the external pressure is compensated forup to a flight altitude of approximately 2,000 metres above sea level(FL65). Above this altitude the internal pressure is kept constant. Anactual altitude protection case occurs if the cabin pressure thatcorresponds to an atmospheric pressure at FL65 drops to the ambientpressure of the aircraft. This is the case for example

-   -   during sudden failure of the cabin pressure supply;    -   if the pressure cell sustains damage;    -   in the case of loss or damage to the cockpit cover; or    -   in the case of an emergency exit by means of the ejection seat.

In such altitude protection cases the airtight bladders 4 expand untilthe pressure equilibrium with their surroundings is restored. In thisprocess the tension pocket 2 and the pressure pocket 3 have differenteffects on the organism of the person wearing the G-suit 1.

FIG. 1 b shows the altitude protection device at an atmospheric pressurecorresponding to an altitude of 5,500 metres above sea level (FL180). Atthis pressure the bladder 4 in the pressure pocket 3 has approximatelytwice the volume it does at sea level. Consequently the pressure pocketexerts less of a pressure force onto the abdominal cavity of the wearerand in this way supports pressure breathing. This expansion has nosignificant influence on the circumferential tension of the G-suit 1.

At this altitude the tension pocket 2 on the back of the G-suit 1 isjust about filled. The expansion of the bladder 4 placed in said tensionpocket 2 also leads to a small increase in pressure in the interior ofthe G-suit 1, but it does not yet lead to a significant increase in thecircumferential tension of the G-suit. When the environmental pressureis further reduced the tension pocket 2 with the bladder 4 expandingtherein acts as a linear actuator whose cross section gradually becomescircular, thus increasing the circumferential tension of the G-suit 1 byshortening the circumference.

FIG. 1 c shows the altitude protection device at maximum effect at anatmospheric pressure as encountered at maximum operational altitude ofthe aircraft, for example at an altitude of 19,800 metres above sealevel (FL650). Both bladders 4 completely fill their pockets 2, 3 andare prevented by said pockets 2, 3 from expanding any further, even ifthe ambient pressure continues to drop.

The altitude stated in this first exemplary embodiment, at whichaltitude the tension pocket 2 begins to function as an actuator,represents a physiologically sensible example but it is in no waymandatory. In normal operation, at regulated cabin pressure, the memberof the crew is not to be impeded by the altitude protection device andis to have full mobility. The inventive step also covers other exemplaryembodiments with other behaviour when experiencing a change in pressure.The volume relationships of pockets 2, 3 and bladders 4 can be adaptedto various aircraft with different cabin pressure levels and differentmaximum operational altitudes. It is not mandatory for the bladders 4 toattain their maximum volume at the same pressure.

In a way that is adapted to the altitude, the altitude protection deviceprovides the performance required to prevent hypoxemia. For example, upto an altitude of 5,500 metres above sea level, pressure breathing isincreasingly supported in that the pressure in the abdominal cavity andthe lungs is increased. From this altitude onwards, as the environmentalpressure further drops, there is in addition direct compression of thetorso region by way of the tension pocket 2 that acts as a fluid muscleor a linear actuator, and there is indirect compression in the entireregion of the G-suit 1, which indirect compression spreads by way of theliquid-filled additionally tensioned veins 6. The environmentalpressure, which is increased in the entire region of the G-suit 1, alsoacts against the decompression syndrome and, at altitudes from 19,200metres above sea level (FL630) onward also against ebullism, theoutgassing of bodily fluids. Certain aircraft attain maximum operationalaltitudes of up to 23,000 metres above sea level (FL750).

The bladders 4 can be designed as certified disposable bladders, whichrenders the altitude protection device extremely fault-resistant whilealso rendering it essentially maintenance-free.

FIG. 2 shows a first exemplary embodiment of a bladder 4. This bladder 4is made from an elastic material, for example PU. The integrated knitteddistance fabric 5 defines a minimum volume of air or gas that is takenup by the bladder 4 in its relaxed state, as shown in FIG. 2 a. At abase altitude, for example at sea level, the pressure in the interior ofthe bladder corresponds to the external pressure while the bladder 4 isin its non-expanded and relaxed state, directly adjacent to the knitteddistance fabric 5. FIG. 2 b shows the same bladder 4 at higher altitude,i.e. at lower external pressure. The elastic bladder 4 is stretched andnow takes up a volume that is larger than the minimum volume.

FIG. 3 shows a second exemplary embodiment of a bladder 4. The bladder 4comprises an elastic middle bridge 7. The middle bridge 7 divides thebladder 4 into two intercommunicating chambers with the same pressure,each comprising a knitted distance fabric 5. The middle bridge 7 leadsto a delayed expansion of the bladder 4 in the plane of the bridge.Depending on the thickness and the design, elastic elongation of themiddle bridge 7 only commences from a definable ambient pressure. FIG. 3a shows the variant with a middle bridge 7 in the relaxed state at sealevel pressure; FIG. 3 b at commencement of elongation of the middlebridge 7; and FIG. 3 c at maximum expansion of the bladder 4 with themiddle bridge 7 elongated to the length of the diameter. One or severalmiddle bridges 7 or other punctual or line-shaped elastic connectingparts of the top and bottom of the bladder 4 can be used in a targetedmanner to cause expansion of the pressure pockets 3 and the tensionpockets 2, which expansion is not directly proportional to theatmospheric pressure.

FIG. 4 shows a third exemplary embodiment of a bladder 4.

The bladder 4 is connected to an additional bladder 9 by way of aninelastic line 8. This additional bladder 9 has been placed into aninelastic additional pocket 10. This additional pocket 10 is connectedin a non-positive manner to the line 8. In the additional bladder 9, asin the bladder 4, a minimum volume is defined by the knitted distancefabric S. The additional pocket 10 is situated outside the G-suit 1. Theelasticity of the additional bladder 9 can exceed that of the bladder 4.As the ambient pressure drops, first the very elastic additional bladder9 expands into the additional pocket 10. The volume of the bladder 4 isessentially unchanged. As soon as the additional bladder 9 has attainedits maximum volume, i.e. as soon as it completely fills the additionalpocket 10, any further pressure equalisation can only take place by wayof expansion of the bladder 4. In other words the expansion is delayedand is greater than where there is no additional bladder 9 because alarger quantity of air becomes effective, namely the total quantity ofgas that at the base height is contained in the bladders 4, 9 that areopen in the knitted distance fabrics, as well as the gas that iscontained in the line 8.

In a variant of this exemplary embodiment the additional volume merelycomprises the line 8 which for example is a plastic pipe. Since theadditional volume is defined in a fixed manner by a rigid inelastic pipethat under the influence of the forces and tensions encountered hardlyundergoes any changes in cross section, the quantity of gas contained inthe additional volume or in the additional volumes immediately andwithout any delay fully contributes to building up the tensile stressgenerated by the bladder 4. The additional volumes are placed on theoutside of the G-suit 1 in such a way that they restrict and impede themobility of the wearer as little as possible, even in their inflatedstate.

Apart from a simple and cost-effective manner of producing the altitudeprotection device according to the invention, said altitude protectiondevice provides a great advantage in that there is no need for anadditional garment, for example in the form of a jacket, which wouldunnecessarily constrain the wearer, and furthermore, in that from thepoint of view of energy and function said altitude protection device isindependent and requires no connection lines whatsoever to the aircraftor to the ejection seat.

1. An altitude protection device for members of the crew ofhigh-performance aircraft as a supplement to an acceleration protectionsuit according to the hydrostatic principle (G-suit (1)), whichcomprises a high-strength stretch-resistant woven textile fabric,comprising liquid-filled veins (6) that extend essentially along theentire length of the G-suit (1), characterised in that they comprise: atleast one tension pocket (2) made from a textile fabric withcharacteristics that are comparable to those of the G-suit (1), whichtension pocket (2) at least along both edges that extend essentially soas to be perpendicular to the direction of tension is in a non-positiveway connected to said G-suit (1) so that inflation of the pocket (2)leads to a reduction in the distance of these vertical connections; ineach case at least one gas-proof bladder (4) for each tension pocket(2), comprising an elastic plastic material; at least one pressurepocket (3) made of a stretch-resistant textile fabric, which pressurepocket (3) is attached on the inside on the G-suit (1) along a line thatis arranged so as to be perpendicular on the direction of tension sothat inflation of the pressure pocket (3) does not result in anysignificant change in the circumferential tension of the G-suit (1); andin each case at least one gas-proof bladder (4) for each pressure pocket(3), comprising an elastic plastic material.
 2. The altitude protectiondevice according to claim 1, characterised in that the bladders (4), ofwhich there are at least two, comprise a knitted distance fabric (5),which allocates to them a predetermined minimum volume even undermechanical load.
 3. The altitude protection device according to claim 2,characterised in that there is precisely one tension pocket (2) with onebladder (4), which tension pocket (2) is attached to the back piece ofthe G-suit (1) in such a way that it comes to rest between the veins (6)that extend on the rear of the G-suit (1), and that there are preciselytwo pressure pockets (3), each with a bladder (4), attached in thestomach region on the inside of the G-suit (1).
 4. The altitudeprotection device according to any one of claims 1 to 3, characterisedin that the tension pocket (2), of which there is at least one, at sealevel is partly filled by the bladder (4) arranged inside it, and thusthe bladder (4) when the ambient pressure decreases first fills in thevolume of the tension pocket (2) before its expansion leads to asignificant increase in the circumferential tension of the G-suit (1).5. The altitude protection device according to any one of claims 2 to 4,characterised in that at least one bladder (4) comprises at least onebridge (7), which, when the bladder (4) is subjected to increasedpressure, delays the expansion of said bladder (4) in the bridge plane.6. The altitude protection device according to any one of claims 1 to 5,characterised in that the tension pocket (2), of which there is at leastone, and the bladder (4) contained therein are dimensioned such that thetension pocket (2) significantly contributes to an increase in thecircumferential tension of the G-suit (1) only from an atmosphericpressure that corresponds to an altitude of between 5,500 metres abovesea level to 7,600 metres above seal level.
 7. The altitude protectiondevice according to any one of claims 1 to 6, characterised in that thetension pocket (2), of which there is at least one, and the pressurepocket (3) of which there is at least one, as well as the bladders (4)contained therein, are dimensioned such that the tension pockets (2)essentially attain their maximum volume from an atmospheric pressurewhich corresponds to the maximum operational altitude of the aircraft.8. The altitude protection device according to any one of claims 1 to 7,characterised in that at least one bladder (4) is connected to anadditional volume arranged outside the G-suit (1), wherein, when theambient pressure drops, this additional volume remains constant from thepoint of reaching a predefined ambient pressure, and, furthermore, thequantity of gas contained therein essentially contributes entirely tobuilding up tension in the bladder (4).
 9. The altitude protectiondevice according to claim 8, characterised in that the additional volumearranged outside the G-suit (1) comprises an additional elastic bladder(9) that is accommodated in an additional pocket (10) made from astretch-resistant textile fabric, and comprises a line (8), wherein theline (8) connects the additional bladder (9) with the bladder (4). 10.The use of an altitude protection device according to any one of claims1 to 9 as altitude protection for crew members of high-flying aircraft.